Has Putin Broken International Law?

President Barack Obama has said that Russian President Vladimir Putin has violated international law by sending troops into the Crimea. Law is on Obama's side, which is why Putin is organizing his justification counter-offensive.

Putin's forces were apparently concerned enough about the U.N prohibition to strip the identifying markers off Russian soldiers before sending them into Crimea, and to now call these troops "local defense forces." But removing their insignias does not change the facts.

Putin's new tactic is to claim that Russia has been invited in. It is illegal to invade another country, but not illegal to send in help when a legitimate government requests it. Putin has asserted that Ukraine's ousted president, Viktor F. Yanukovych, remains the Ukraine's legitimate president, and he has asked for help. Putin may also be behind the influx of protest tourists to Ukraine who pretend they are Ukrainians asking for Russian help.

There is a long and storied tradition of governments inventing a legal premise to justify their actions. During the Cold War, President Reagan justified U.S. intervention in Grenada as necessary to protect Americans living on the island. Reagan also defended U.S. military support in Nicaragua as collective self-defense requested by El Salvador. These claims were just as credible as Putin's claims, which is to say: not very.

Putin cares little whether his actions violate international law. But the Europeans and Americans who will organize a response do care, and ordinary Russians may also care, which is why Putin is working to create the appearance of legal intervention. While only the U.N. Security Council (where Russia holds veto power) can authorize a collective response to Russian aggression, the legal principle of "responsibility to protect" allows individual states and groups of states to legally justify their response to illegal acts of aggression.

Where might all this lead? The answer depends on who ends up ruling Ukraine. And this is the point. Each side is now wooing its future dance partner: Americans and Europeans are wooing Ukraine's pro-Western political forces, and Putin is stirring fears of ethnic Russians and seeking support for a pro-Russian government.

An anti-Putin Ukrainian government could try to bring a case to the International Court of Justice over the illegal use of force in Russia's incursion into Crimea. This is the strategy Georgian leaders tried after Russia's last foreign intervention, but the effort failed. Since Russia does not accept the International Court of Justice's general jurisdiction, Georgia instead charged Russia with the illegal use of force, and with violating the International Convention on the Elimination of all forms of Racial Discrimination, which Russia has ratified.

The ICJ rejected jurisdiction in the case, however, because without Russia's preconsent the ICJ could not decide claims about illegal force. For the racial discrimination convention, Georgia would have to first try to negotiate with Russia over its disagreements. Any Ukrainian government would find itself similarly hampered.

Imagine that an anti-Russian Ukrainian government gained power and actually won its legal suit. Then what? In the best-case scenario, Ukraine would win a legal declaration on its side, which might make Russia liable to compensate Ukraine for its losses. Russia could then refuse to comply, or it could do what the United States did to settle the illegal use of force suit that Nicaragua won in front of the ICJ. Russia could require that Ukraine relinquish its claim if it wants to receive its aid package. And Ukraine would have few options, since ICJ rulings can only be enforced by the Security Council (again, on which Russia holds veto power).

A more likely scenario is that the issue will never get this far. Even if an anti-Putin government wins the upcoming election, Ukraine is still too dependent on Russian energy to antagonize it by bringing a legal suit that will achieve so little.

The International Criminal Court is not likely to become involved, in any event, since neither Russia nor Ukraine have ratified the Rome Statute, which would give the International Criminal Court the right to claim jurisdiction over the case. Nor would the Security Council refer the matter to the court.

The reality is that international law has little to offer right now. This will only be the case, however, as long as Russia does not engage in mass atrocities; these would change the political calculus

Human rights violations can be pursued by Ukraine's new government, or by individuals raising legal claims in front of the European Court of Human Rights, where both Russia and the Ukraine are signatory members. Russia actually has a good record for paying awards ordered by the European Court of Human Rights.

At this point, international law's largest contribution may be to channel Russia's response. International law is leading Putin to step back from the more overtly illegal strong-arm tactics associated with sending in troops, and he knows that any mass atrocities would provoke a more serious international response.

International law won't stop an invasion, and in light of the events in Syria, odds are that neither side wants to escalate to the point of mass atrocities. So international law stands ready on the sidelines, a tool of both sides to justify their actions.

- Karen Alter is a professor of political science and law at Northwestern University.